BACKGROUND Atropinization of the sound eye is an alternative to patching in the treatment of amblyopia. Whether atropine treatment can induce a switch in fixation depends on the refractive error of the sound eye, visual acuity of the amblyopic eye, distance from the fixation target, and presence of any optical correction or penalization. General guidelines are needed on the basis of refractive error and visual acuity in the amblyopic eye to predict which patients may potentially benefit from atropine penalization. METHODS Refractive error and visual acuity at distance (6 m) and/or at near (33 cm) were recorded in a normal eye of 126 consecutive children (mean age, 8.2 years), 30 to 60 minutes after receiving cyclopentolate 1%. Visual acuity was plotted versus refractive error at distance and at near, and best-fit curves were calculated. RESULTS There was a consistent, reproducible relationship between refractive error and visual acuity after cycloplegia at both distance and near in healthy children. CONCLUSIONS The results of this study can be used to quickly determine whether atropine penalization has the potential for success on the basis of a patient's visual acuity in the amblyopic eye and refractive error in the sound eye. When adequate hyperopia is present in the sound eye, one should consider testing for fixation preference or initiating a therapeutic trial of atropine. Those children with insufficient hyperopia in the sound eye relative to visual acuity in the amblyopic eye can be spared the time, expense, and potential side effects of atropine penalization.